Are you injured?
I've been lucky with injuries throughout my athletic career. More than often, my biggest complaint is chronic soreness cured by a few days rest. By the end of the summer I had A LOT of low back pain. I dialed down my training and started stretching like a mad man but but it never got better.
Fast forward to mid-October, after visiting a sports chiropractor I had started to feel better (he told me I needed to stabilize and strengthen my abs--and I agree it was an area I had neglected). I should've knocked on wood after telling my chiro that I felt great. I re-injured myself doing Back Squats and thought my days of heavy lifting were over.
I looked all over the CrossFit message board for people who were dealing with the same issues. It turns out, I was not alone and I found a link to a post from Mark Rippetoe that offered a solution to my problem. I used this protocol and felt better after 10 days and was back in the gym working hard after two weeks (PR'ed Jackie by 44 seconds!) I think my injury was a result of weak abdominals, poor sitting position (have you ever seen the way lifeguards sit in their stands), overstretching, and not enough consistent strength training. I'm working on fixing these things to avoid anymore speed bumps in my training.